1. Field of the Invention
The present invention relates to a process and an apparatus for highly efficiently producing furnace carbon black having desired physical properties useful for applications as filler material, reinforcing material, conductive material, coloring pigment, etc.
2. Description of the Related Art
For producing furnace carbon black, it has been common to introduce an oxygen containing gas and a fuel in the axial or tangential direction of a cylindrical carbon black production reactor, and while transferring the high temperature combustion gas formed by the combustion to a down stream reaction zone, introduce a hydrocarbon feedstock into the high temperature combustion gas stream to form carbon black. However, the thermal decomposition reaction of the hydrocarbon feedstock is complicated, and it has been difficult to form carbon black having desired physicochemical properties with high efficiency.
Especially, to efficiently mix, contact and react the high temperature combustion gas stream formed in the first reaction zone with the hydrocarbon feedstock introduced in the second reaction zone, is regarded as an important factor governing the production efficiency and the properties of the resulting carbon black. Heretofore, for mixing and contacting the high temperature combustion gas with the hydrocarbon feedstock in the second reaction zone, it has been attempted to increase the kinetic energy by giving a strong swirling motion to the high temperature combustion gas, or by modifying the shape of the throat of the second reaction zone. However, no adequately satisfactory results have been obtained. For example, Japanese Examined Patent Publication No. 27112/1980 discloses a process for producing carbon black, which comprises forming hot gas streams divided outwardly and inwardly in the circumferential direction with the reactor axis at the center, and supplying the hydrocarbon feedstock from the axial direction. However, the hot gas stream divided and introduced outwardly, is intended just for the protection of the reactor wall and accordingly will be a cause for substantially reducing the yield of carbon black. Besides, with the introduction of the divided streams from the tangential direction to the reactor axis to the circumferential direction, it is impossible to obtain a highly turbulent flow at the throat. Further, the feedstock supply nozzle is held on the reactor axis, and when the nozzle is moved to control the physicochemical properties of the resulting carbon black, it is necessary to protect the nozzle with a cooling jacket, whereby an extra heat loss is brought about. Besides, with the introduction of the feedstock from the nozzle provided on the reactor axis, it takes time for the diffusion of the feedstock in a radial direction, whereby effective mixing can not be conducted at a high speed, and a reduction in the yield of carbon black is unavoidable.
Further, Japanese Examined Patent Publication No. 45581/1980 discloses a process for producing carbon black, wherein air for combustion is preheated by heat exchanger with the reaction product after quenching, for heat recovery, and a part of the preheated air is supplied to the reactor as an independent divided stream for the protection of the reactor wall. However, in this process, the introduction of the feedstock is limited to the center portion around the reactor axis, and no high temperature combustion gas stream will be formed along the reactor wall, whereby formation of a high temperature turbulent flow region essential for conducting the thermal cracking of the hydrocarbon feedstock with high efficiency, will be inadequate. Besides, the hydrocarbon feedstock is supplied from a feedstock supply nozzle in an axial direction held in the high temperature reactor, whereby it is necessary to provide a cooling jacket for the protection of the nozzle, thus leading to an extra heat loss. Furthermore, since the feedstock is introduced from the reactor axis, it takes time for the diffusion of the feedstock in the radial direction, whereby effective mixing can not be conducted at a high speed, thus leading to a decrease in the yield of carbon black.
Still further, Japanese Unexamined Patent Publication No. 183364/1986 discloses a process for producing carbon black by means of a carbon black production reactor, wherein a combustion chamber is provided with a gas inlet directed in a tangential direction, wherein a feedstock is introduced into its throat in a direction traversing the gas stream for thermal cracking. However, the high temperature combustion gas stream is a swirling stream, and it is incapable of forming an adequate high temperature turbulent flow region at the throat i.e. at the supply point of the feedstock, whereby it is impossible to form carbon black with high efficiency.
Japanese Examined Patent Publication No. 6203/1972 discloses a process for producing carbon black, wherein turbulence is created by a plurality of burners disposed at an angle of from 10 to 80.degree. to the reactor axis, and a hydrocarbon feedstock is supplied to intersect the turbulence. However, the reactor having the burners attached thereto has a truncated cone shape with its cross-sectional area gradually increasing towards the throat (diaphragm), whereby the turbulent flow obtained by the intersection of the combustion mixture streams diminishes towards the throat, whereby the turbulent flow energy of the combustion mixture streams and the turbulent flow energy obtained by the shape of the throat are not utilized effectively. Further, the introduction of the hydrocarbon feedstock is in the axial direction of the reactor, whereby the introduced hydrocarbon feedstock is obliged to diffuse in the radial direction of the reactor, and it is impossible to introduce the hydrocarbon feedstock swiftly and collectively to the area where the turbulent flow energy is maximum. Accordingly, the control to obtain a carbon black having optional desired properties, is very difficult, and it is particularly difficult to produce carbon black having a small particle size.
Further, in Japanese Examined Patent Publication No. 10581/1987, a plurality of carbon black intermediate gas streams formed separately, are collided with each other. However, the collision in this case is collision of carbon black intermediate gas streams themselves after introduction of a hydrocarbon feedstock, and the turbulent flow energy by the collision does not serve for efficient formation of carbon black. Further, the convergence of carbon black intermediate gas streams is conducted by an assembly of at least two first and second reaction zones, and it is likely that the carbon black intermediate products have already formed before the assembly. Consequently, the physical properties (quality) of the carbon black product tend to substantially vary. Further, if the number of series for the assembly increases, an increase of the surface area of the main body of the reactor is unavoidable, whereby the heat loss from the surface of the reactor increases, and the energy efficiency decreases.